Among solid-state light emitting devices, light-emitting diodes (LEDs) have electrical and optical advantages such as low energy consumption, long service life, good stability, small size, fast response, and stable luminous wave length. LEDs and related light-emitting systems are widely used in fields such as illumination, household appliances, displays and signage. This type of light-emitting devices and systems have had remarkable progress in improved lighting efficiency and service life, and therefore are promising to become the mainstream for a new generation of lighting.
To improve light-emitting efficiency of the LED, a substrate transfer technology has been developed in recent years. The transfer processes may include: depositing a GaN-based thin film over a sapphire substrate via MOCVD, bonding the GaN-based thin film to the semiconductor or metal base using wafer bonding technology or electroplating technique, and removing the sapphire substrate using laser lift-off (LLO) method; and fabricating the device into a vertical structure. FIG. 1 is a structural diagram of a conventional vertical LED, comprising: a conductive substrate 100, a light-emitting epitaxial layer including a p-type semiconductor layer 121, an active layer 122 and an n-type semiconductor layer formed on the conductive substrate 100 via a high-reflection P-type conductive bonding layer 110, thereby forming a vertical structure LED with current injection into an N electrode 131 and a back electrode 132. In packaging this LED device, in general, welding is performed with silver paste die bonding or Au—Sn eutectic soldering. The N electrode is to be wire bonded to a support structure, and the N electrode on the light-emitting surface blocks a large amount of emitting light and is detrimental to light extraction.